뇌 자기공명영상에서 Quiet-T2 기법을 이용한 소음감소의 유용성
Usefulness of Acoustic Noise Reduction in Brain MRI Using Quiet-T2
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뇌 자기공명영상(Magnetic Resornance Imaging; MRI)에서 검사 중 발생되는 소음을 줄이기 위한 기법으로 경사파형을 변경한 Quiet T2-weighted Turbo Spin-Echo(이하 Q-T2)와 일반적으로 사용되는 T2-weighted Turbo Spin-Echo(이하 T2) 영상의 소음수준 및 영상의 질을 비교하여 그 유용성을 알아보고자 하였다. 3.0T MR 기기로 뇌 MR 검사를 받은 60명(남자 29명, 여자 31명, 평균 연령 60.1세)의 환자를 대상으로 하였다. Q-T2와 T2 각각의 영상에서 소음 및 심박동수를 측정하였다. 정량적 분석은 Q-T2와 T2의 SNR, CNR, SIR 값을 측정한 뒤 독립표본 T검정을 이용하여 통계적 분석을 하였다. 정성적 분석은 Q-T2와 T2의 전체적인 영상의 질에 대하여 육안으로 평가하였다. 평가는 5점 척도로서 우수(excellent) 5점, 양호(good) 4점, 보통(fair) 3점, 불량(poor) 2점, 평가불가(unacceptable) 1점으로 평가하였다. Q-T2와 T2 검사 중 평균소음과 peak소음은 Q-T2가 기존 T2에 비해 각각 15dBA, 10dBA 감소하였다. 또한 각각의 검사 중 120초 동안 심박동수의 평균값은 Q-T2에서 더 낮은 값으로 나타났지만 통계적인 유의성은 없었다. 정량적 분석의 결과 CNR과 SIR은 유의한 차이가 없었으며, SNR은 Q-T2가 더 낮은 평균값을 보임으로서 유의한 차이를 보였다(p<0.05). 정성적 분석은 59개의 Q-T2와 T2 영상의 질이 동일하게 우수(excellent) 5점으로 평가되었으며, 1개의 영상에서 모션 아티팩트로 인해 양호(good) 4점으로 평가되었다. Q-T2는 기존의 T2와 같이 검사시간 및 진단의 정확도는 동일하지만 소음을 효과적으로 감소시킬 수 있으며, 이로인하여 환자 편의를 향상시킬 수 있을 것으로 사료된다.
Abstract
Acoustic noise during magnetic resonance imaging (MRI) is the main source for patient discomfort. we report our preliminary experience with this technique in neuroimaging with regard to subjective and objective noise levels and image quality. 60 patients(29 males, 31 females, average age of 60.1) underwent routine brain MRI with 3.0 Tesla (MAGNETOM Tim Trio; Siemens, Germany) system and 12-channel head coil. Q-T2 and T2 sequence were performed. Measurement of sound pressure levels (SPL) and heart rate on Q-T2 and T2 was performed respectively. Quantitative analysis was carried out by measuring the SNR, CNR, and SIR values of Q-T2, T2 and a statistical analysis was performed using independent sample T-test. Qualitative analysis was evaluated by the eyes for the overall quality image of Q-T2 and T2. A 5-point evaluation scale was used, including excellent(5), good(4), fair(3), poor(2), and unacceptable(1). The average noise and peak noise decreased by 15dBA and 10dBA on T2 and Q-T2 test. Also, the average value of heartbeat rate was lower in Q-T2 for 120 seconds in each test, but there was no statistical significance. The quantitative analysis showed that there was no significant difference between CNR and SIR, and there was a significant difference (p<0.05) as SNR had a lower average value on Q-T2. According to the qualitative analysis, the overall quality image of 59 case T2 and Q-T2 was evaluated as excellent at 5 points, and 1 case was evaluated as good at 4 points due to a motion artifact. Q-T2 is a promising technique for acoustic noise reduction and improved patient comfort.
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